I have some left over concrete I figure making concrete blocks and shooting them might be fun. The difference between screwing off and science is taking notes. So I need to select a testing size and concrete to water ratio and cure time to be consistent. The cure time needs to be the same on all samples and at least a month long. Do basic tests to figure out which type of admixes with cheap consumer concrete resists the negative effects bullets tend to have on concrete. Compare the the different admixes to the more expensive ones, using the same cheap concrete prepared appropriately for the application. Figure out which one does the best over all, and best overall cost wise if there is much difference. Then try to make it better I'm looking for affordable, off the shelf addtives or reinforcement that make concrete stronger. Searching around most interest is in making concrete more wear resistant not more penetration resistant so no easy internet answers. The thing that makes the concrete stronger has to be economical. Making this strength needs to be cheap. Eventually use higher grade concrete with 2 or 3 modifications. Then make larger heavier samples and hit them with bigger rounds to reflect real world events, aka going full scale. The things that I would like to test to make the concrete stronger are mixing steel with the concrete like including layers of chicken wire, stucco mesh, increasing density with vibration, vacuum to reduce air entrapment, mixing water soluble polymer hardener commonly used in tile mortar, surface treatment like epoxy, aggregate modification such as mixing broken ceramic tile, glass, volcanic material, engineered synthetic fibers, water reducers, fumed silica, plasticizer or just adding more Portland cement to make it stronger like they did in the old days. Then test combinations of the above if they show a positive result and see if individual improvements have increasing or diminishing returns when used together with the cheap concrete. Again the thing that gets mixed with concrete needs to be cheap and the method needs to scale up, for example removing the air from a yard of concrete via vacuum, I don't know how I would scale that up at the moment but I think it could be done. Or I might not be able to find enough broken tile to make a difference in an actual build. Poly hardener may be just too expensive to use to mix up in say 5 to 8 yards of concrete. This isn't a post about " build a wall this thick to stop this kind of round" to me a test like that is utterly useless. I don't know what you local building codes are like, I don't know what the design your PE signed off on looks like I don't know you're trying to build. So I can't say "build a wall like this". Due to the unlimited number of combinations of form types, thicknesses, construction methods out there I think this is as close to one size fits all as I can get. What say you? The beauty of my testing concrete sample testing is it could be used for anything. You can see what standard concrete will do compared to standard concrete plus something that can be affordability added to a larger scale concrete job. Want to build a survival dome, or some kind of small above ground shelter yep. Want to build a standard building with 4 inch walls and want to add something in the forms in addition to rebar to make it stronger, this applies to that. Making something out of concrete blocks and want to fill in the blocks with something better than standard concrete, yeah I'm testing medium workability small aggregate mixs that could flow into the block voids. Using ICFs and can only use 4 to 6 inches of thickness so it obviously doesn't look like a fortress and want stronger than standard concrete, that's in here. Build something out of concrete using standard forms that's really strong that doesn't look like a fortress, yeah. Calling a concrete truck and want to add something to the mix before they pour, yeah I'm testing several things like that. Live off grid and can only work with what you can carry in on the back of your 4x4 pickup and calling in a concrete truck is out of the question, yeah this might give you a few ideas. Want to make pre-cast panels you can build something out of or fortify an existing structure, well yeah. Update edit. Poly hardener test, even as little as 25% will make your concrete a little stronger. Additional cost: $75 per yard. 50% poly booster helped even more for double the price. Is it worth it? I don't really think so. Stucco mesh 1 and 2 layer tests. Putting 1 layer of stucco mesh in the middle of the form works pretty well, but does not appear to be the best use of the mesh. Putting layers just below the inner and outer surfaces worked best. The stucco mesh held on to loose aggregate that normally would have been blasted away, the mesh retained most of the loose aggregate and disrupted the bullet before it hit solid concrete. A very cool result. I believe the additional cost was around $30 per layer per yard for a 4 inch wall. Is it worth it? It would appear so. Recommended use is at least 1 layer of stucco mesh on the outer surface and use larger aggregate. Definitely going to test this full scale. Also much cheaper plastic mesh preformed almost well, which cost $7 per yard, per layer in a 4 inch wall. The high velocity ejected material damaged the plastic mesh on the strike face side much worse than the steel mesh. The plastic mesh cast inside and on the back side the form seemed to do about as well as the more expensive stucco mesh. Need to test these both full scale. Vacuum concrete sucked. It did far worse than the control. Don't use vacuum concrete. Vibrated concrete did the same or worse than control samples. Don't vibrate concrete to make stronger, only do long enough to fill voids. Looks like air entrapment is pretty important. Polymer strength booster at 50% mix had some effect. The cost of wetting concrete with 50% poly booster is around $150 per yard. 25% poly booster was almost no different than the control. Spend your budget on something else. If you are trying to make the ultimate concrete and money is no object and you cant put any more steel in your forms and have a bunch of fiber in there, mesh too, sure use it in at least 50% concentration. Its just a lot of money for such a small improvement. Initial results look like adding something to the concrete that isn't a concrete ingredient such as steel mesh is the most effective use of funds. According to quikcrete they are saying their concrete weighs 4,500lb per yard, before you add water. Then to make it wet 1 yard needs up to 200lb of water. Here is a mix ratio quick reference. M is the number of mega pascals. Then cement : sand : gravel (by volume) M10- 1:3:6 M15- 1:2:4 M20- 1:1.5:3 M25- 1:1:2 M30- 1:1.5:1.1 Large agg needs to be angular and 10mm, 0.3:1 water to cement ratio by volume. 1 Mpa is equal to about 145psi. When I go full scale I think I will use ammo cans as giant measuring cups.